The prior art cited in the above said parent applications are herewith incorporated by this reference. They are Beuther, et al, U.S. Pat. Nos. 3,997,431, 3,940,330, and 3,840,473; Huntley 3,184,415; Fredricksen 3,464,930; Oga, et al 3,544,617; Hinden, et al 3,945,946; Cull, et al 4,039,478 and Japanese Pat. No. 775,809 (translation in file of parent application, Ser. No. 874,753). The aforesaid parent applications are incorporated herein by reference, and are referred to for further details of the disclosures in the aforesaid prior art.
The prior art relating to hydrodesulfurizing catalysts is extensive. The catalysts which have been sold and used in commercial processes for desulfurizing of petroleum distillates and residual oil have been based on a substrate made by calcining alumina hydrates for example, pseudoboehmite. The calcined pellet has been treated with solutions of salt which on calcination are converted into their oxides. These salts are those of metals of the Group VI and Group VIII metals. In the case of a widely used catalyst, the metals are molybdenum usually combined with nickel. The present state of the art includes as useful metals such as cobalt in addition to Mo and also in addition Mo and nickel. Iron has also been suggested as useful metal in combinations with molybdenum.
In such combinations, it has been proposed in the prior art to add a compound metal of the Group IV-B to the pellet, which has been treated with the above salts, as a promotor. The metal, e.g. titanium is employed as the tetrachloride in heptane solution and applied to the substrate to which the molybdenum and nickel has been applied and after calcination of the substrate containing the molybdenum and nickel salts. See Beuther U.S. Pat. No. 3,840,143, cited above.
The product thus produced is stated to place the titanium as a mono-layer on the substrate containing the Mo and Ni. See Frayer, U.S. Pat. Nos. 3,968,027, 3,968,028, 3,068,029. See also, Beuther U.S. Pat. Nos. 3,840,473 and 3,846,285.
As has been disclosed in our U.S. Pat. No. 4,018,714, the problem with incorporating titanium in an alumina substrate, useful in formulating hydrodesulfurizing catalysts, as for example as shown in the above Beuther patents, arises from the use of acidic titanium salt solutions. As disclosed in said U.S. Pat. No. 4,018,714, the non-acidic titanium compound, in the form of an organo titanium salt is added to the alumina pellet. The disclosure of said patent is incorporated herein by this reference. In our U.S. Pat. No. 4,196,101, cited above, this problem is solved by employing a non-acid compound of titanium, specifically titanium hydrate either added as such to the hydrated alumina or to generate the hydrate in situ in the alumina hydrate water mixture. The titania hydrate-alumina hydrate water mixture may then be converted into a shaped form herein referred to as a pellet. The said copending applications are incorporated herein by this reference. Such pellets may be used to produce catalysts, by incorporation of catalyst compounds into the mixture of hydrates prior to shaping, or the shaped pellet may first be dried and calcined prior to impregnation with catalytic compound to form, for example, hydrodesulfurizing catalysts of good abrasion resistance and crush strength.
It has been suggested to form a hydrogenation catalyst for unsaturated and aromatic hydrocarbons from a mixture of alumina hydrate, titania hydrate, iron sulfide and molybdenum desulfide and at least a few percent of water (Johnson, et al, U.S. Pat. No. 2,649,419).
Molybdenum disulfide is reported to sublime at 450.degree. C., which is substantially less than the temperature we have found is desirable to calcine the pellet that is at a temperature and for a period sufficient to convert the hydrates into oxides and to dehydrate the pellet and produce the desired crush strength and abrasion resistance.
Such catalysts may not be subjected to calcination at temperatures in substantial excess of 450.degree. C. to produce substantially anhydrous pellets of sufficient structural strength. We employ the metals, in the form of oxides, together with the titania. The Group VIII metal compound, and Group VI metal compound are employed in the form to produce an oxide on the degree of calcination, desired to produce the physical properties of the pellet. These oxides are stable at temperatures of calcination and at temperatures of use. Thus, we may develop the desired physical properties and retain the catalytic component in the pellet, i.e. the oxides of the Group VIII and Group VI metals.
In the process of the prior art which involved the use of solutions of molybdenum salts or of mixed molybdenum and cobalt or nickel salts, for incorporation into alumina substrates, there is a serious problem of instability of the solutions of the molybdenum salts and complexes used in the impregnation of alumina substrates. The problem associated with the incorporation of these metal salts in concentrations to produce the necessary loading in the substrate, is the difficulty of keeping the molybdenum in solution in sufficiently high concentration, especially in the presence of cobalt or nickel compounds. This difficulty limits the concentration of the salts and the order of application of the compounds.
It is well known that the solubility of the molybdenum or the molybdenum-cobalt or molybdenum-nickel complexes can be made sufficient to hold a relatively high concentration by various expedients. See Molybdenum Chemicals Series, issued by Climax Molybdenum Company, Bulletin Cdb-16, dated January, 1973, and entitled, "Aqueous Solutions of Molybdenum Compounds for Catalysts Application". One of the expedients is the incorporation of the phosphate ion into the solutions. See British Pat. No. 701,217, published Dec. 23, 1953; Pessimisic, U.S. Pat. No. 3,232,887; Colgan, 3,287,280; Jaffee, 3,544,452; Adams, 3,629,146; Mickelson, 3,755,148, 3,755,150, and 3,755,196; Colgan, et al, 3,840,472; Feins, et al, 3,897,365; and Brown, et al. 969,280.
While the above prior art teaches the incorporation of the phosphate ion into the impregnating solution, employing alumina as a substrate in the production of hydrodesulfurization catalysts, it has been stated in the prior art (see Beuther, U.S. Pat. No. 3,840,473) that the presence of a phosphorous or phosphate level approximately 2% by weight in a titanium bearing alumina pellet is completely unacceptable in a titanium promoted Group VIII and Group VI metal bearing hydrodesulfurizing catalyst.